Walker had his own bid for the Republican nomination for president, but withdrew from the race early on.

Months before other Republicans began to coalesce against candidate Donald Trump, Walker urged his opponents to drop out as well and to rally around a candidate to take on the businessman for the nomination.

“After eight years of the failed Obama-Clinton Administration, Americans are looking for real leadership and a new direction. Ted Cruz is a principled constitutional conservative who understands that power belongs to the states – and to the people – and not bureaucrats in Washington,” Walker said in a statement released as he announced his decision on Sykes’ show. “Just like we did in Wisconsin, Ted Cruz is not afraid to challenge the status quo and to stand up against the big government special interests. He is the best-positioned candidate to both win the Republican nomination and defeat Hillary Clinton. That’s why I endorse Ted Cruz for President of the United States.”

Walker said, “I just fundamentally believe that he is a constitutional conservative,” in addition to favorably comparing Cruz’s style and policies as more suitable to the middle of the country.

“I wanted to make sure I was supporting someone I wasn’t against someone,” Walker said. “I want to be for something”

USA Today has more:

Cruz is “the best positioned by far” to defeat Donald Trump for the Republican presidential nomination and to win a general election over Democrat Hillary Clinton, Walker told Wisconsin radio talk show host Charlie Sykes.

“We want people who are principled, common sense conservatives,” Walker said.

The Wisconsin governor also praised the Texas senator as a “constitutional conservative” who is willing to take on “the big special interests,” even if they are aligned with Republican interests.

Cruz, who worked for the endorsement, had said Tuesday he is “a big, big fan” of the governor, and that he is a “true conservative.”

His support as a successful GOP governor in an otherwise blue state may swing some fence-sitters who have yet to make a decision. Walker won three gubernatorial elections in four years—including a recall—and could help the senator navigate the Republican primary.

Cruz, for his part, appears to have adopted some of Walker’s style. The senator has emphasized that the 2016 race for the White House will come down to three things: jobs, freedom, and security. Walker similarly emphasized the issues of growth, reform, and safety during his short-lived bid on the trail in Iowa.

While Walker’s favorability numbers have hovered below 40 percent statewide in polling after his exit from the 2016 race, he remains widely popular among Republicans and his actions still attract attention from conservatives across the country. With one week remaining until Wisconsinites vote—and fewer than four months remaining until this summer’s convention—Walker’s decision comes at a crucial time.

The Wisconsin primary could help prevent Trump from securing the party’s nomination before the convention or it could make any chance of a contested convention increasingly unlikely.

Trump tried to pre-empt the endorsement on Twitter yesterday.

“After the way I beat Gov. Scott Walker (and Jeb, Rand, Marco and all others) in the Presidential Primaries, no way he would ever endorse me!” Trump tweeted Monday.